Vertically oriented pumps that pump liquid from a lower level to a higher level are well known. Both positive displacement and centrifugal or turbine-type pumps have been successfully used for such purposes for many years. Often such pumps may be used only intermittently, and they may need protection from their liquid environment when not in use to avoid encountering undesirable corrosion or wear or, in some cases, to prevent them from being rendered inoperable due to deposits or other effects of the environment during the inactive periods.
Typical of the pumps that need protection when not in use are those employed as emergency pumps for fire extinguishing apparatus on coastal facilities or offshore platforms. In a typical platform used for offshore oil drilling operations, a fire extinguisher pump may not be needed for months (or even years), and, thus, it may remain idle during a long period of time. However, when a fire breaks out on such a platform, it constitutes one of the most hazardous and time-critical emergency situations that may be encountered. To avoid disastrous consequences, it is necessary to quickly provide a means for delivering very large quantities of sea water at high pressures sufficient to reach all elevations and spaces on the platform.
Since platforms may extend fifty to a hundred feet (or even higher) above the ocean surface, the need for reliable, high pressure, high volume water pumping systems is apparent. Unfortunately, if the pump and associated gear have been idle in the water for a substantial period of time, there is a grave risk that their water delivery capability may have been severely impaired or even destoryed in the interim. This may result from a number of factors, including corrosion, deposits of foreign matter or clogging or fouling with seaweed or other plant life. A very common problem has also been the fouling of pumps by growths or layers of animal life (especially mollusks), such as mussels and similar shellfish, which attach themselves tenaciously to exposed inlets and interiors as well as to exterior portions of pumps and lines that are left submerged in the water.
Whatever the cause, even heavy-duty pump systems may be found to have been rendered totally inoperable at the critical time they are needed to fight a fire due, for example, to the pump impellers becoming immovably fouled or locked.
It has been contemplated to alleviate the risk of loss of pumping capacity by several methods. For example, the pump may be mounted well above the high water line on the platform, and a suction line or tube can be extended from the pump down into the water. However, while this will protect the pump itslef, it is unsatisfactory for most uses because it risks becoming inoperable at critical times due, e.g., to a loss of vacuum in the suction line, the necessity for priming the pump, the need for a strainer at the foot of the suction line, and the like. Moreover, this technique still risks the fouling or clogging of the suction line, and it cannot function at all in areas where tide differentials exceed about thirty feet.
It has also been contemplated to position the pump below water level, but to mount it on a pivoting frame so that it can be pivoted up out of the water when it is not in use. This, however, presents other problems and risks due to the potential failure of swivel joints, supporting means, and drive mechanisms, as well as the risk of undue delay in getting the pump positioned in the water during the critical early moments after the outbreak of a fire.
There has thus been a long felt need for a submerged pump assembly, and a method for adapting submerged pumps to overcome (or at least greatly alleviate) these and other problems of the prior art. It is an object of the present invention to achieve this result.